As is understood, soil is an important building material. It serves as the base for virtually all pavements, tunnels and buildings, and thus, can be thought of as an element used in construction. In construction, soil will typically be specified to have certain minimal mechanical properties, e.g., dry density, resilient modulus and strength. While some testing can be conducted in a laboratory, e.g., to determine the suitability of a raw material or blend of materials, it is also typical to perform field tests to assess the soil selection or composition, to determine appropriate site-specific compaction specifications, and to monitor for in-process quality control of the degree of compaction that affects mechanical properties of interest, typically a specified void (as reflected in density) ratio or resilient modulus.
As is understood by those skilled in the art, soil used to fill or level a construction site must be compacted, typically by the application of vibratory energy and weight, in order to obtain the requisite density and modulus. Sometimes, contractors over-compact soil as each of successive layers are added in order to ensure that the result will meet the requisite specification when completed. The ability to quickly and reliably test soil properties could significantly reduce costs due to unnecessary over-compaction and avoid long-term settlement problems due to spatially non-uniform compaction.
U.S. Pat. No. 6,604,432 discloses a “Soil Compaction Measurement” wherein a man-portable device characterizes the stiffness and inferred modulus of the soil over the recently compacted ground. The device excites the ground by a dynamic force supplied by a “shaker” and then measures the applied excitation force and the motion of the ground in response to the applied force. Appropriate processing is used to derive ground stiffness and inferred modulus of the material under the measurement instrument. In order to conduct a survey over a large area of recently compacted soil with this device, individual measurements must be made at many representative points. This can consume a significant amount of time depending upon the size of the area being surveyed.
Improved soil compaction measurement devices are therefore desired, which facilitate the measurement of soil compaction over an extended area.